Petr, I also am not sure what you mean by ET.
The terms I am familiar with are backspacing and offset, which are somewhat related. This thread
http://forums.amceaglesden.com/index.php?topic=18694.0indicates the backspacing (measured from the back of the rim to the mounting surface) of the stock rims was 4.5".
Offset measures the mounting surface in relation to the centerline of the wheel (as in a cross-section of the wheel, not through the bore hole). If the mounting surface is closer to the front of the wheel, it is a positive offset. If the mounting surface is closer to the back of the wheel, its a negative offset.
Here is a link to specs on Jeep wheels, which are similar to Eagle wheels. This indicates that the center bore is 71.5 mm.
http://www.wheelhelp.com/Jeep_Bolt_Patterns.htmI have the American racing #AR895 on my Kammback in the 16x7 size. They worked great. I think I have 215/70-16 tires on them. I believe I tried 215/75 and there would have been some rubbing which would have required some trimming, so I didn't go for the bigger size.
Good luck!